Spark-gap apparatus



Apr; 10, 1923.

v 1,451,426 1.. J. LESH SPARK GAP APPARATUS Y Filed Apt. 9', 1918 4- sheets-sheet 5 WITNESSES v QJ/VVENTOR.

WQW Mad-47* ATTORNEY.

Apr. 10, 1923. 1,451,425

I L. J. LESH SPAR GAP APPARATUS".

YF il-ed Apr. 9, 1918 4 sheebs-5sheet-4 I {/VVENTORI A TTORNEYH,"

LAWRENCE J. LESH, OF NEW YORK, N. Y.,' ASSIGNOR TO EMIL J. SIMON, OF NEW Patented Apr. 10, 1923.

I YORK. N. Y.

. SPARK-GAP 'APPARATUS.

Application filed April 9,1918. Serial No. 227,440.

a .T all whom it may 607106771! Be it known that I, LAWRENCE LnsH, a. citizen of the United States, residing at New York city, in the county of New York and State of New York, have invented certain new'and useful Improvements in Spark- ,Grap Apparatus, fully described and repre- .sented in the. following specification. and

the accompanying drawings, forming a part More particularly the invention relates to spark gap apparatus of the multiple unit gap type, and the invention aims generally to provide iin-.

proved apparatus of this type of a simple and compact construction and which shall provide for convenient and ready removal .and replacement of the spark gap unlts and for convenient adjustment of the circuit for 8 connecting any desired number of'the units features of construction, arrangement and combinations of parts herein disclosed and specifically pointed out in the claims.

and any desired group of the units in the circuit, and to provide an improved spark gap unit. The invention consists in the As a full understanding of the invention can best be given' by a detail description of an approved construction embodying the various features of the invention and certain modifications thereof, such a descrip- "tionwill now be given in connection with the accompanying drawings. in which Fig.1 1S a'view in front elevation of a multiple unit spark gap apparatus made in accordance with the invention, only part *ofthe whole number of spark gap'units being shown in'position in the holders;

Fig.2 is a section taken on a horizontal plane indicated by the line 2-2 on F ig. 1: Fig. '3 is a side'view of the apparatus with the contact arms in a different position from that shown in Figs. 1, 2 and 1:

Fig. 4 is a partial rear view of theapparatus showing the adpustable contact arms and the contact knobs which are connected -'with the gap holders, the contact arms being in the position of Figs. 1 and 2':

Figs. 5, 6 and? are detail sectional views illustrating the actionof the contact pieces carried by the contact arms;

Fig. 8 is a face view ofthe inner face of a gap plate of'one of the unit spark gaps;

Fig. 9 is a central sectional view of one of {the unit spark gaps; and

Fig. 10 is an edge View of a spark gap unit provided with heat dissipating ribs.

Referring to the drawings, and first to Figs. 1 to 7, the apparatus shown comprises a plurality of unit spark gaps 10, and holda ing and circuit controlling apparatus there for. The parts of the apparatus are mounted on a support 11 which is most desirably in the form of a fiat board or plate of bakelite delecto or other suitable insulating material and which is usually mounted in vertical position on the instrument board either in or'opposite. an opening through which portions of the apparatus extending from the rear side of the support may extend be- .yond the rear side of the instrumentboard.

The support is most desirably mounted 'on the instrument board so that it may be readily moved to give access to parts of the apparatus on the rear side of the support,

and for this purpose the support in the construction shown has at its lower edge a hinge connection to the instrument board, as in-' dicated at 12, so that it may be swung forward and downward from the position shown in Figs. '1 and 3, being normally held "in operative position by a suitable catch or holding means 13.

' The unit spark gaps may be of any suitable construction, for example, as shown in U. S. Patent No. 1,253,103 granted to E. 1

Simon January 8,1918. Most desirably, spark gaps embodying the features of the invention as illustrated by the gap shown in Figs. 8 and 9are employed. The gap shown in these figures, which'is a single sparking space unit, although features of the invention embodied therein are ob viously not limited to a single sparking space, or two-plate,gap, comprises two flat electrode plates 15 and 16 of heat-conducting and electricity-conducting material which 'll'lay he of circular: orother suitable form,

each plate being 'formedat its inner face witli'a flat central seat to which is secured 'an electrode orsparking plate 17 and with an annular bearing face 18 surrounding the electrode and separated therefrom desirably by an annular channel '19.",Tlie

plates are securedtogether with an annular gasket 20 of fish paper impregnated with 1 sparking space.

linseed oil and beeswax or other suitable insfilating and air-excluding material, be-

tween theirbearing faces by means of screw bolts 21, each of which is screwed into 0ne of the plates and has its head seated in a bushing 22 of insulating material seated on the other plate. The bearing faces of the gap plates are desirably grooved to provide oneor more narrow annular ribs 23,-wh1ch, bearing against the gasket 20, increase the assurance of exclusion of air from the The electrodes 17 may be riveted or otherwisesecured to the electrode seats of the gap plates and in the assembled gap have their sparking faces parallel and spaced slightly apart to provide the necessary sparking space between them.

It will be noticed that in the construction shown the screw bolts 21 by which the gap plates are forced and held pressed against the interposed gasket 20 to set the plates the proper distance apart and to form the air--;

tight joint are located inside, or within, the outer portions of the bearing faces 1 8. By thus locating or arranging the clamping devices to exert their pressure on the plates at a point or points within the outer portions of the bearing faces of the plates and interposed gasket, the ditliculty which has been experienced in assembling the plates of spark gaps in which the clamping devices exert their pressure outside of or beyond the outer circumferential portions of the bear ing faces of the plates is avoided. Vith my construction, the'itightness withjvhich any one of the screw bolts 21 is .set td'hold the adjacent portions of the plates together is not affected by the tightening or loosening of any other of the screw bolts. Most. de-

sirably, in order to avoid the possibility of access of air to the sparking space through the screw bolt openings, the screw bolts are located with relation to the bearing faces so that the bearing faces extend inside of as well as outside of the screw bolts, thus providing a continuous seal between the sparking space and the screw bolts.

The center of the electrodes proper, or sparking plates, is most desirably removed so as to providesparking plates and sparking surfaces of annular form. as shown in Figs. 8 and 9. I have found that the use of such annular electrodes results in the voltage remaining constant under a longer continued operation than when the center of the electrodes is not removed. This improved result is probably due to the fact that the use of sparking plates of this form avoids. or at least reduces. the warping or buckling of the plates resulting from the actioga of heat on metals of dissimilar co-efficients of expansion, and also possibly to the better discharge of heat from the plates.

The sparking plates or electrodes should be made from a metal of high thermal and electrical condutivity, plates of silver being usually used. The gap plates on which the electrodes are mounted are usually made of brass or other metal of suitable strength and not too expensive.

Extending from the face of the support 11 are a plurality of holders, each adapted to receive and hold a single spark gap unit. Each holder comprises a pair of spring conducting arms 25 and 26 forv bearing on opposite sides of the spark gap unit, the arms being desirably formed with knobs or bosses to .extend into recesses 27 formed in the .gap plates for more securely holding the gap while yet permitting its ready removal and replacement when desired and the outer ends of the arms of each holder are bent outwardly to permit the gap unit toibe more readily entered between them. The electrical connections to the gap units when in position in the holders are made through the holder arms, and the holders are connected in series, the' adjacent arms of adjoining holders being electrically connected, as by forming such adjacent'arms of adjoining.

holders of a single piece of metal bent into U form, the connecting portion of the metal, or plate 28, between the two arms providing means for conveniently securing thearms to the support 11 by means of screws as shown. The arms of each holder are insulated from each other when a gap is'in position between them except for the sparkin moval of the spark gap unit from any holder the circuit will be closed between the two supporting arms of the holder, this resultbeing secured in the construction shown by having the holder arms set under such spring tension that the arms of each holder will bear against each other when there is nothing interposed between them. The outer arm of the end holder of each row of holders is secured to the support by means of a flange or plate 28 at its inner end screwed or otherwise secured to the support.

Inthe construction shown in Figs. 1, 2 and 3. the holders are arranged to support the spark gap units in two parallel series or rows, the gap units being supported to stand vertically and perpendicular to the support 11 in horizontal rows, one above the other. This arrangement of the gap holders to support the gap units in rows or series in which the units stand flatwise to each other and spaced apart has the advantage that it provides for the free moveg action across the gap. WVhen all the holders ment of air between the gap units and consequent cooling of the units; and having-the holders arranged. to so support the gap units vertically inhorizontal rows has the further advantage that as the'units become heated an upward flow of air between them is induced,

For further providing against an undue increase in temperature of the spark gap units in operation, the outer surfaceiof the gap platesis desirably formed with parallel ribs 29 to provide an increased heat dissipating surface, asfshown on one. of thegep units in Fig. 3 and onthegap unit. shown in Fig. 10; The gap units should be placed in the holders turned so that these cooling ribs-extend vertically, and inorder that the ribs shall not-interferewith. the placing of the gap units inthe holders and their removal therefrom, the ribs are cutaway at in order thatcircuit connections may be made to include in the operatingcircuit any desired number of the holders and spark gap units carried thereby, connectionis made from each of the plates orportions 28 and :28'and 28 beinglconnected to its -,own cor-5 28 by-meansof a connector 30 toone of, Y

material, The shaft37 has surroundlng its a s'eries of contact terminals 31, each plate responding. terminal, except that the plate 28 at theright hand end of the upper rowof holders is connected to the, sameterminal as the plate 28 at the right hand endof the lower row of terminals, this connection thus to a single contact terminal in thesame man-v ner that adjacent arms of'other adjoining holders of the series are connected toia single contact terminal. The outer arms of the end holders at the lefthand end'of the two rows, which holders are the end holders of "the whole series, are connected to separate terminals 31. a

. The terminals 31 are arrangedin a circular series on the rear side of-the supportll, and

in 'the constructionshown are of ball orv rounded knob form, having stems extending through the support 11 to connect with the respective connectors 3,0,the1support being formed, as before stated, of-a plate of suit- "I provide for making connection to the gap able insulating material. The means which holders through theterminals 31'andf0r varying such connections, is arranged topernut not only of varlation 1n the number of gaps connected in the operating circuit, but

353m .36 mountedtoiswing, about a commonaxis located centrallyv of the. series of contact terminals 31, and means for swingm said arms either separately-or together.

he contact arm 35 is carried byahollow shaft 37 which extends through the support ll and is journaled,atitsforward or front end in a cross-bar 38 carried by side pieces 39 extending forwardfrom thesupport '11.

The contactv arm 36 is carried by ashaft 40 which extends through and is fitted to turn withintheshaft 37. The shaft 37 carries at its outer end in front o f i thev cross-barf38 ,a hand wheel 41 by which the shaft and the contact arm 35 maybe turned; andthe shaft 40; carries at its outer end in front of thewheel 41 a hand wheel 42 by which the shaft 40 and the contact arm 36 may be turned.

' Thecontact arms 35 and 36 are made of conducting material and 'are insulated from each otherin the construction shown by forming the shaft 40 of bakelite delecto -or other suitable non-conducting material. The shaft 37 is also inthe construction shown and most desirably made ofnon-conducting nection is made by a conductor 47 Y to a con- .ductin rod 48 extending through and to the rear 0 the support 11 and'ca'rrying a terminal 49, For securing goodcontact with the bearing ring'46, the conductor 47 is formed with a ring which, surrounds the shaft 37 and is screwed or. otherwise secured to the end of the bearing ring 46. Connection from a one side of the circuit is made to thefterminal 49 and fromthe other side of the circuit directly to the arm 36 In order that circuit conncub sfcb the terminal 49. and the contact arm 36 may be automatically made by the actof placing the support 11 in position for operation of the device andv broken by removing the support from such'position, that is, in the construction shown, by swinging the support into the .position shownin Figs. 1 and 3 or forward and downward from such position in order to give access to parts of the apparatus on the rear side of the support, yielding con- .tact pieces 50 and 51 are provided mounted in position to make contact with the terminal 49. and with the arm 36 respectively when the apparatus is inoperative position.

These contact making parts are most desirably of ball and cup form as shown, thecontact pieces 50 and 51 having recessed contact faces, and the terminal 49 being shaped to fit the recess of the contact 50 and the arm 36 having its hub or axial portion 52 formed to provide a terminal shaped to fit the recess of the contact piece 51. The contact pieces 50'and 51 in the construction shown are carried by spring pressed rods mounted in housings 53 and 54 respectively carried by posts 55, one of which is shown in Fig. 3, to the base of which posts the circuit wires 56 and 57 are connected.

The contact arms and 36 car: each a spring pressed contact piece 60 and 61 respectively for making contact with the terminal knobs or balls 31. The contact piece 60 is carried by a spring pressed rod mounted in a housing 62 carried by arm 35, and the contact piece 61 is carried by a spring "pressed rod mounted in a similar housing 63 carried by the arm 36. Each of the contact pieces 60 and 61 is formed with a 'concave or cup-shaped bearing face to fit down over the convex outer faces of the terminals 31 so as to give an extended contact and also so that the contact piece thus formed and spring pressed shall serve to accurately position the contact piece with respect to any terminal 31 and yieldingly resist turning movement of the contact arm from any position of contact. The contact pieces and the terminals being formed with co-acting positionlng faces, will thus serve to indicate manuallyto the operator turning the wheels 41 or 42 when either arm has been moved into position to bring its contact piece into register with and proper contact relation I with any desired terminal 31.

In order that the slight resistance to turning of the wheels 41 and 42 which serves as a manual indication of correct position of the contact arms shall occur only when an arm has been moved to bringits contact from which it is being moved.

Referring to Figs. 5, 6 and 7, Fig. 5 shows a contact piece in engagement with a terminal 31. Fig. 6"shows the position of the contact piece when the arm 35 has been moved to carry the contact piece half the distance for bringing it into engagement with an adjacent terminal. In this position the contact piece has been pressed back against the pressure of its spring by riding up on the face of the terminal, the contact piece being held in this position by engagement at one side with a high point of the terminal from which it is being moved and having also come into engagement on its other side with a high point of the terminal into contact forming engagement with which it is being moved. By continued movement of its carrying arm, 'the contact piece is then carried on over the new terminal, and as it moves over such terminal is advanced by its spring until it is brought into the desired contact forming relation with the new terminal as shown in Fig: 7. The pressure of the contact piece against the inclined face of the far side of the terminal after it has been moved somewhat from the position shown in Fig. 6 serves to aid in the completion of its positioning movement and insures its reaching the desired position from which further forward movement is then resisted by the engagement between the inclined faces of the contact piece and. terminal. In this shifting movement of the contact piece from one terminal to an adjacent terminal no forward movement of the'con'tact piece in the space be tween the terminalshas been permitted, and, therefore, no resistance to the turning of the contact arm takes place except when the contact piece is positioned properly with respect to one of the terminals 31. .T he operator in turning either one of the hand wheels 41 or +12 can, therefore, always tell from the turn ing resistance of its hand wheel when either of the contact pieces is inproper engaging position with one of the terminals.

A distance piece extending from the shaft 40 to the housing 63 carried by the contact arm 36 and formed of or having an engaging portion of insulating material serves by engagement with the end of the arm 35 to limit the approaching movement of the two arms. The engaging portion 66 of this distance piece may be formed to extend to any desired extent according to the minimum distance to which the approaching movement of the two arms is to be limite As shown, see Fig. 4. the engaging portion 66 is so formed that when the arms have been moved toward each other tothe limit of their approaching movement there will be one terminal 31 between the engaged terminals; that is, so that there must always be at least two spark: gap holders included in'the operating circuit The distance piece 65 in the construction shown serves also as a steadying arm for the sleeve 63, which is supported by the arm 36 at a point 'near its rear end. A. stop 67 formed in the construction shown by a stud extending rearward from the supporting plate 11 serves to prevent movement of the contact arms 35 and 36 beyond their respective positions'for engagement with the res ective end terminals 31 of the series.

en the contact arms 35 and 36 are in the positions shown by Figs. 1,2 and 4, the

de ight gap "holders of the 'upper row will be connected in the spark gap ci'rcuit.-the-circult then extending from the wire 56 through the spring contact piece-'50. terminal 49, rod

- 48; Connector etT, arm 35 and its contact piece 60to the'terminall31 which is connected to.

the outer arm of the gap holder at the lefthand end-of the upper row of holders. viewing "the same'from the front of the apparatus as itap'pears in Fig. l; thence through the the circuit extends through its" connector 30 to its terminal 31 with which the contact piece'*'61- is in" engagement; and thencev through the contact piece 615-arm 36. spring "contact -51and its "housing'and post to-the circuit'wi're 57; If the gap 'hol'dersof the upper row are each provided with a. gap

unit,'thiere will thus be eight gap units con- 'nected 1n series. If. oneo'r more otthe ;h'olders"is not provided with a gap unit. the

units in the remaining holders of the upper row will nevertheless'be connected in series in the'circuit,the circuit being then completed across the empty holders by engagement of their spring holding arms. v

7 By turning the arm 36 in either direction from the position shown in Figs. 2 and et while the arm remains stationary, the number of gap'holders connected n thecir-v cuit may be increased or decreased according to tie direction in which the arm 36 is turned; and if the arm 35 be turned while;

'cate the location of the. series or group of gap holders connected in the circuit.

the arm 3G remains stationary, tlie number of holders connected in the .circuit will also be, correspondingly changed. By turning both arms together without changing theirrelatii e angular relation.the connections will be shifted so as to change the particular series orv group of gap holders included in the circu t without changing thenumber of holders in- ,cluded. The desired shifting of the contact arms either relatively or together is readily accomplished by means of the hand wheels 41 and '42. the resistance or feel of the wheels indicating to the operator when the contact arms are in proper contact making position, as already explained. I

In order to aid the operatorin making thedesired adjustment of the gap connections. suitable position indicating means for indicating visually the position of thecontact arms is desirably provided in connect1on'w tlrtliehand wheels 41 and 4L2. n the (.ODStIllCtIOH shown. such means LOIH- prises an indicating disc which is mounted'in front of the cross piece 38 and to-the- ;oearing faces.

.vided with an indicatingmark shown as having an arrow associated with it. Thearrows on the disc 70 and on thehand wheel .42 are so placed-relatively to thercontact arms controlledby the two. hand wheels that the relative position of the arrowswill in dicate at all times the relative'positions of the contact arms: and the numbers onthe discTO are spaced according to the spacing of the contactterminals 3lso thatthe position of thearrow or other mark on the wheel 12 'with relation to the numbers on the disc TOAvillJindic-ate the number of gap holders connected in thecireuit, For example, when the contact arms are in the position shown in: Figs..2 and 4;, in which 8 gap holders are connected in the circuit, the markon the ;hand wheel e12 will indicate the number 8011 the disc 70. If one or the other oftheha'nd' wheels is 'turned'to move its contact ar m relatively to the other contact arm so-asto, conhand wheels be moved. together so as to shift I the contact arms without changing the numher-of gap=holders connected in the circuit, the relation .of the indicating mark on the hand-wheel 42 to the number series on the disc'will not'change, but the shittingof the disc and the position of the series'of numbers between, the arrow on the disc and the indicating mark on the wheel 42 will indi- \Vhile in the construction shown the gap unit holders are connected in the circuit in series. the feature of the invention relating to the selective connection of the holders in the circuit is obviously not limitedin its ap-" plication. merclyto arrangements in which the holders are connected in the circuit in series-connected groups; and it is also to be understood that this selective connection feature of the invention is not limited to spark gap units as the only electrical eleflat-wise with their sparking. faces spaced apart to provide a spark gap space between them. said plates having bearing faces extending about their sparking faces and being secured together with an insulating and air excluding packing between their hearing faces by a plurality of clamping devices arranged about the sparking faces of the plates but within the outer portions of their 9.. Aspark vgap unit, comprising a plurality of electrode plates assembled together plurality of gap unit holders each .formed fiatwise with their sparking faces spaced apart to provide a spark gap space between them, said plates having bearing faces extending about their sparking faces and being secured together with an insulating and air excluding packing between their bear ing faces by screw bolts located in holes in the plates opening through their bearing faces at points intermediate the inner and outer portions of the bearing faces.

3.Spark gap apparatus, comprising a plurality of gap unit holders each having spring contact pieces to bear against opposite sides of a gap unit, said contact pieces of each holder being under tension to bear against each other to close the circuit at the holder when there is no gap unit in place therein, and electrical connections between the holders.

4. Spark gap apparatus, comprising a plurality of gap unit holders electrically connectedin series, each holder being formed of a pair of spring conducting arms to bear against and support a gap unit and through which electrical connection is made to the opposite sides of the gap unit, said spring arms being under tension to move into engagement with each other and close the circuit across the holder when there is no gap unit in position in the holder.

- 5. Spark gap apparatus, comprising a plurality of gap unit holders each formed of a pair of spring conducting arms to bear against and support a gap unit and through which electrical connection is made to the opposite sides ofthe gap unit, the spring arms of each holder being under tension to move into engagement with each other and close the circuit across the holder when there is no gap unit in position in the holder, a terminal connected to the outer arm of each end holder and other terminals connected each to the adjacent arms of two adjoining holders, and contact means for making contact with said terminals to connect the holders in the circuit, said contact means being "adjustable for varying the number of gap holders connected in the circuit.

6. Spark gap apparatus, comprising a of a pai'ro'f' spring conducting arms to bear against and support a gap unit and throughwhich electrical connection is made to the opposite sides.of the 'gap'unit, the spring arms of each holder being under tension to move into engagement with each other and close the circuit across the holder when there" is no gap unit in position in the holder, a terminal connected to the outer' arm of each end holder and other terminals connected each to the adjacentarms of two adjoining holders, and contact means" for making contact with-said terminals to. con- 1 nest the holders in thecircuit, said contact means being adjustable for varying the number of gap holders connected in the circuit and for connecting in the circuit any desired series of the gap holders.

7. Spark gap apparatus, comprising a plurality of gap unit holders, a plurality of terminals through which connections may be made for connecting different numbers of said holders in circuit, contact members for making circuit connections to sald terminals, coaxial shafts mounted one within the other, connections between said shafts and said contact members, and means for turning said shafts either together or one relatively 'to the other for moving said contact members relatively to said terminals to vary the number of the gap holders connected in the circuit and for connecting in the circuit any desired series of the gap holders.

8. Spark gap apparatus, comprising a support, a plurality of gap unit holders mounted on the front side of the support, a plurality of terminals mounted on the rear side of the support through which connections may be made for connecting different numbers of the gap unit holders in the circuit, coaxial operating shafts nr'ounted one within the other and extending from the front to the rear side of the support, contact members for making circuit connections to said terminals, connections for controlling the position of said contact members relatively to said terminals by the turning of said shafts, and operating means we carried by said shafts at their forward ends whereby the shafts may be turned either from therear to the front side .of the support, contact arms carried one by each; of said shafts, a spring contact piece carried by each of said arms for making contact with said terminals, and hand pieces carried by said shafts at their forward ends whereby said shafts may beturned sepa- 9 rately or one relatively to'the 'otl1er,"sa id telrrniinals and. said: \contact pieces being formed with. coacting positioning faces whereby the proper positioning of'the contact-pieces with relation to any terminals will be aided and wi e manually indicated t0 he. operator. 1 i,

10. Spark gap-apparatus, comprising a! I pluralityof gap unit holders, a plurality of terminals through which connections may be- 9 said holders in'circuit, saidterminals-being arranged in a curve of constant radius,con-..

tact arms mounted to turn on a common; axis and each having a. contact partfor making contact with said terminals, and means for turning said arms either together or one relatively to the other to connect in the circuit any desired'series of sa-id holders or tovary the number of said holders connected' 'in the circuit. 11. Spark gap apparatus, comprising a pluralityof gap'unit holders, a'plurality of. terminals through which connections may be made for connecting different numbers of 'sa-id'holders in circuit, and "a spring contact fpiece movable withrelation to'theterminals for varying the number of holdersconnected in the circuit, said terminals and saidcontact piece being formed with co-acting-positioning faces permitting aforv'v'ar'd movement of the contact piece understhe pressureof its spring when'it is positioned with respect to any one "of the contact terminals,-said-parts being formed to prevent such for-w'ard move ment of the contact piece in any intermediate position betweenadjacent terminals; 1

12. Spark gap apparatus, comprising a terminals through which connections may be made for connecting different numbers of holders in circuit, said terminals being spaced at approximately equal distances apart in a line or series, and-a springpressed contact piece movable relatively to the line or series of terminals, said terminals. and said contact piece being'formed one with a convex contact face and the otherwith a concave contact face, and the contact piece having bearing portions at opposite sides of its contact face so formed that the bearing portion on one side of its contact face will, when the contact piece is being moved from one terminalyto' an adjacent terminal, come into engagementwith the adjacent terminal while the contact piece is held pressed back against the pressure of its spring by the engagement of its other bearing portion with the terminal from which it is being moved. 13. Spark gap apparatus, comprlsing a plurality of gap unit holders, a plurality of contact terminals through which connections may be made for connecting different numbers of the gap unit holders inthe circuit, hand operated circuit controlling means adjustable to var the number of holders connected in the clrcuit and for connecting any desired series of theholders inthe circuit,

said .means including means Qfor manually indicating the" contact making positions thereof, and means for indicating visually the number of holders connected in the circuit.

l4. Spark gap apparatus, comprising a comprising hand pieces movable together or relatively to eachother, and apart mounted to move with one of said hand, pieces and marked to indicate accordingto the relative "positionfof the hand pieces thenumber of holders connected in the circluit, H 15. Spark gap apparatusnmomprising a -plurality .ofgap, unit holders, circuit con-- trolling means for selectively connecting said gap unit holders in the circuit comprising members movable relatively to each other to vary the number; of holders. con- @nected inthe circuit and movable together for connecting in the circuit any desired series of said holders, hand pieces mounted toxturn' on a common axis and, by the turn- .ing movement of which the position of said membersmay he'adjusted, and a disc mounted to move with one of said hand pieces and markedto indicate according to the relative position of the hand. piecesthetnumberof holdersconnected in the circuit.

of contact terminals through which connec-' 'tions may. be made for connecting different numbersofthe holders in the circuit, contact members formaking circuit connections to said terminals, coaxial. shafts mounted one within the other, connections for controlling the position of said contact members relatively to said terminals by the turningof saiii shafts, and hand wheels carried one by each of said shafts at one end thereof and mountedclose together to permit them to be grasped and turned together or to be turned separately, one of said hand wheels having number markings associated therewith, and the other hand Wheel having an indicator associated therewith, whereby the number ofholders connected in the circuit will be indicated according-to the-relative positions of the hand wheels; 2' I 17. Spark ap apparatus, comprising a supporting p ate of insulating material, a pluralityof gapunit holdersmounted on the front side of thesupporting plate, a. plurality of terminals mounted on the rear side of the supporting plate through which connections may be made for. connecting diiierent numbers of the gap unit holders in the circuit, said terminals being arranged in a curve of constant radius, coaxial shafts of non-conducting material mounted one within the other extending through the supporting plate, .a contact arm carried by each of s'aidshafts. having a contact part for -making contact with said terminals, a cirplurality otgap unit holders, a plurality of cuit connection. directly to the contact arm 16. Spark gap-apparatus,comprising a v carried by the inner shaft, a metal sleeve on the outer shaft to which the contact arm carried by the outer shaft is connected, a metal bearing ring mounted on the supporting plate through which the outer shaft extends and in which said sleeve is journalled, and a circuit connection to said bearing ring at the front side of said supporting plate.

18. Spark gap apparatus, comprising a plurality of gap units having electrode plates the outer faces of which are formed with parallel ribs providing an extended heat dissipating surface, the gap units being mounted in a horizontal row in which each unit stands in vertical position flatwise to adjacent units with its heat dissipating ribs extending vertically and in which the units are spaced apart to permit an upward flow of air between them.

19. A spark gap unit, comprising a pair of electrode plates assembled together fiat-' holders on the front side of the supporting plate, circuit controlling means for variably connecting said gap unit holders in the cir cuit mounted on the rear side of said supporting plate, and operating means for said circuit controlling means mounted on the front side of said supporting plate.

21, Spark gap apparatus, comprising a hin ed support, a plurality of gap unit holders mounted on the front side of the support, circuit controlling means for variably connecting said gap unit holders in the circuit mounted on the rear side of the support, operating means for said circuit controlling means mounted on the front side of the support, means for holding the support support is moved into its operative position.

22. Spark gap apparatus, comprising a hinged support, a plurality of gap unit hol ers mounted on the front side of the support, circuitcontrolling means for variably connecting said gap unit holders in the circuit mounted on the rear side of the support, operating means for said circuit controlling means mounted on the front side of the support, means for holding the support in operative position and for releasing thesu-pport to permit it to be turned into position for access to the rear side thereof, and means for automatically connecting the sparkgap apparatus in the circuit when the support is moved into its operative position, said last mentioned means comprising ter minals extending from the rear. side of thewhen'the support is swung into its operative,- position.

23. Quenched spark gap apparatus .com-

prising a bar of insulating material, a series of metal contact springs secured thereto inspaced arrangement, the fixed ends of successive pairs of adjacent springs being permanently connected electrically, and the free ends of adjacent springs being movable by their resiliency into contact with each other in pairs alternating with thepairs of connected fixed-ends, in combination with gap units insertable between the-pairs of resili' ently contacting spring ends to separate the same and to be resiliently held thereby.

In testimony whereof I have hereunto set my hand in' they presence of two subscribing witnesses.

LAWRENCE J. LEsH.

Witnessesz' ETHEL Jongms, 

